The present invention relates to an implement that is driven by an internal combustion engine, such as an Otto engine having a carburetor. A first control device is provided for controlling engine power and includes a fuel selection device, a butterfly valve disposed in the carburetor, and a connecting element for operatively connecting the fuel selection device with the butterfly valve. A second control device is also provided for terminating ignition.
Such implements can be upright devices or manually guided devices and have the drawback that when ignition is terminated, with the butterfly valve partially or entirely opened, the drive motor continues running due to the momentum of its own mass or that of the movable mass connected thereto, thereby drawing in a certain amount of fuel/air mixture, which is not burned due to the fact that ignition has been terminated. This unburned fuel/air mixture leads to emissions that may not conform to the legal standards, and also to fouling of the carburetor and engine. In addition, when such emissions pass the hot exhaust components, especially when a catalytic converter is utilized, combustion and even explosions result that unnecessarily stress the device and pollute the environment with noise.
This negative effect is particularly critical for implements having a high flywheel mass. Especially with manually guided blowers, the high mass of the fan wheel blower, which without an intermediately disposed centrifugal force coupling is connected directly to the crankshaft, leads to a long slowing time. If during the slowing phase of the blower, while ignition has been terminated, the operator inadvertently operates the butterfly valve, a particularly high portion of unburned fuel is given off through the exhaust.
DE-OS 33 30 994 discloses a fuel valve in the fuel intake that is controlled by the underpressure that exists in the carburetor. Since due to the high rotational speed a considerable underpressure builds up in the carburetor during the slowing phase of the engine, the fuel valve can open unintentionally; the fuel that is drawn in is discharged without being burned.
It is therefore an object of the present invention to significantly limit the supply of fuel of an implement of the aforementioned general type in a straightforward manner when ignition is terminated.